Train PEC Requirements, Prerequisites and Check List

Updated February 3, 2022

The Train PEC button should make training your Paramount’s periodic error correction much easier to perform, it is more reliable than manual collection, and results in optimal tracking performance.

To ensure a successful PEC training, you are responsible for the items in the table below.

The Train PEC button is found on the Telescope window > Tools pop-up > Bisque TCS > Periodic Error Correction tab > Compute PEC tab.

For the best experience, please carefully read and follow the items and explanations below.

ItemExplanation
Ensure the mount is reasonably aligned with the pole A reasonable polar alignment is required so the star does not drift out of the track box while collecting periodic error data. Alternatively, use a TPoint model based on a good calibration data set and enable ProTrack. In addition, you can use TheSky’s Tools menu > Rough Polar Alignment and Accurate Polar Alignment commands to help.
Focus your cameraYour optical system needs to be focused. Hint, use @Focus.
You have recently performed an autoguider calibrationTrain PEC depends on a recent, successful autoguider calibration. Why? For starters, this allows Train PEC to automatically determine if the optical system is mirrored so resultant PEC table is uploaded correctly, allows you the freedom to have the camera rotated at any angle (more below), provides a basis for re-centering the reference star between the Before PEC and After PEC data collection, etc.

Train PEC will not let you continue until you have successfully performed a “fresh” autoguider calibration.
You have selected a suitable reference star Ensure that you have selected a reference star by double clicking the star. For a description of a good reference star, see Choosing a Good Autoguider Calibration Star in TheSky User Guide. Note that the requirements for choosing a reference star for Train PEC are basically the same as choosing the autoguider calibration star.

If you have not already selected a reference star, close this window, return to the Autoguide sub-tab, take a full frame photo, then double click on the desired reference star.

Train PEC will not let you continue until you have selected a reference star by “double clicking” a suitable star on a photo.
You have set a good, short exposure timeMake sure to use a short exposure time, less than or equal to one second, plus ensure the reference star is not too bright nor too dim.

A good “maximum” brightness value for the reference star is in the 1000s. Note the photo’s maximum value is displayed on the Camera window after every exposure to help get this correct. The reference star is too bright if the photos maximum value is near 65000 and too dim if it is under say 1000.
Use a reference star near Dec zero The reference star should be at or near declination zero.

Although stars at higher declinations will give a valid PE calibration, the sensitivity will be compromised.
Use an appropriately sized subframe The default subframe 32 x 32 is typically too small, 100 x 100 or 200 x 200 is normally okay. The subframe size might need to be larger depending on polar alignment, image scale and the number of camera pixels.
The camera may be rotated at any angle Legacy PEC related facilities in TheSky required that the x-axis of the camera be carefully aligned with right ascension/hour angle. This is not a requirement with Train PEC.
The mount can be pointed to either side of the meridianLegacy PEC related facilities in TheSky require you to make a selection as to “Data was collection when mount was pointed west” or not. This is not a requirement with Train PEC and the fore mentioned option is not required/necessary.
Set camera binning to 1 x 1It is recommended to collect PEC data when your camera is at 1×1 binning for the highest resolution. However, Train PEC honor what ever binning you have selected.
Manually enter image scaleMake sure the image scale is accurate/correct on the Periodic Error Correction tab of the Bisque TCS window. Hint, perform a Tools menu > Image Link or create a field of view indicator (FOVI) for your optical system.

Note, image scale must match binning. For example, if image scale is 0.75 arcseconds per pixel at 1 x 1 binning, and you would rather use 2 x 2 binning (not recommended), set the camera binning before entering this window, and set image scale to 1.50 arc seconds per pixel.

Train PEC Will…

  • Collect the Before PEC and After PEC data and display the results, including:
    • Making all the necessary settings to accomplish the task:
      • Disable Direct Guide corrections.
      • Enable camera logging to produce raw tracking logs, not autoguiding logs.
      • Fit a curve to the Before PEC data, re-center the reference star, upload the PEC table to the mount, collect the After PEC data.
      • Automatically turn on Autosave.
      • Graph the results of the before and after periodic error logging session.
    • Each Train PEC run saves all relevant data to a run-specific folder under the camera’s autosave folder.

Additional Information

Click here to see the results of an actual Train PEC run that shows the dramatic improvement of an out of specification worm with 12 arc seconds peak-to-peak periodic error that, after training and periodic error correction is applied, results in essentially no detectable periodic error from the worm/gear train.

Train PEC with a Custom Bisque TCS

To allow Train PEC to be used by a custom, Bisque TCS installation, a file convention is used to dictate PEC parameters so that Train PEC has the data to necessary to operate.

The file must strictly follow the format below for 1) The number of teeth on the HA gear 2) The number of entries in the PEC table 3) The number of arcseconds per motor encoder.

  • Create a file named “PEC Parameters.txt”, in TheSky’s folder.
  • Have the first line in the file be this:
    • “PEC Parameters = nteeth npec upec”
    • For example, an ME II…
    • “PEC Parameters = 576 1125 0.0625”
  • Again, this file must go into the same folder that TheSky is running from (not under “<My Documents>\Software Bisque\…”) but rather “C:\Program Files (x86)\Software Bisque\TheSkyX Professional Edition\”, even if you are running TheSky64.